// queue.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"
#include "queue.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

// this class for use by ByteQueue only
class ByteQueueNode
{
public:
	ByteQueueNode(unsigned int maxSize);

	unsigned int CurrentSize() const
		{return tail-head;}
	unsigned int UsedUp() const
		{return (head==MaxSize());}

	unsigned int Put(byte inByte);
	unsigned int Put(const byte *inString, unsigned int length);

	unsigned int Get(byte &outByte);
	unsigned int Get(byte *outString, unsigned int getMax);

	unsigned int Peek(byte &outByte) const;

	void CopyTo(BufferedTransformation &target) const
		{target.Put(buf+head, tail-head);}
	void CopyTo(byte *target) const
		{memcpy(target, buf+head, tail-head);}

	byte operator[](unsigned int i) const
		{return buf[i-head];}

	ByteQueueNode *next;

private:
	unsigned int MaxSize() const {return buf.size;}

	SecByteBlock buf;
	unsigned int head, tail;
};


ByteQueueNode::ByteQueueNode(unsigned int maxSize)
	: buf(maxSize)
{
	head = tail = 0;
	next = 0;
}

unsigned int ByteQueueNode::Put(byte inByte)
{
	if (MaxSize()==tail)
		return 0;

	buf[tail++]=inByte;
	return 1;
}

unsigned int ByteQueueNode::Put(const byte *inString, unsigned int length)
{
	unsigned int l = STDMIN(length, MaxSize()-tail);
	memcpy(buf+tail, inString, l);
	tail += l;
	return l;
}

unsigned int ByteQueueNode::Get(byte &outByte)
{
	if (tail==head)
		return 0;

	outByte=buf[head++];
	return 1;
}

unsigned int ByteQueueNode::Get(byte *outString, unsigned int getMax)
{
	unsigned int l = STDMIN(getMax, tail-head);
	memcpy(outString, buf+head, l);
	head += l;
	return l;
}

unsigned int ByteQueueNode::Peek(byte &outByte) const
{
	if (tail==head)
		return 0;

	outByte=buf[head];
	return 1;
}

// ********************************************************

ByteQueue::ByteQueue(unsigned int nodeSize)
	: nodeSize(nodeSize)
{
	head = tail = new ByteQueueNode(nodeSize);
}

ByteQueue::ByteQueue(const ByteQueue &copy)
{
	CopyFrom(copy);
}

void ByteQueue::CopyFrom(const ByteQueue &copy)
{
	nodeSize = copy.nodeSize;
	head = tail = new ByteQueueNode(*copy.head);

	for (ByteQueueNode *current=copy.head->next; current; current=current->next)
	{
		tail->next = new ByteQueueNode(*current);
		tail = tail->next;
	}

	tail->next = NULL;
}

ByteQueue::~ByteQueue()
{
	Destroy();
}

void ByteQueue::Destroy()
{
	ByteQueueNode *next;

	for (ByteQueueNode *current=head; current; current=next)
	{
		next=current->next;
		delete current;
	}
}

void ByteQueue::CopyTo(BufferedTransformation &target) const
{
	for (ByteQueueNode *current=head; current; current=current->next)
		current->CopyTo(target);
}

void ByteQueue::CopyTo(byte *target) const
{
	for (ByteQueueNode *current=head; current; current=current->next)
	{
		current->CopyTo(target);
		target += current->CurrentSize();
	}
}

unsigned long ByteQueue::CurrentSize() const
{
	unsigned long size=0;

	for (ByteQueueNode *current=head; current; current=current->next)
		size += current->CurrentSize();

	return size;
}

void ByteQueue::Put(byte inByte)
{
	if (!tail->Put(inByte))
	{
		tail->next = new ByteQueueNode(nodeSize);
		tail = tail->next;
		tail->Put(inByte);
	}
}

void ByteQueue::Put(const byte *inString, unsigned int length)
{
	unsigned int l;

	while ((l=tail->Put(inString, length)) < length)
	{
		tail->next = new ByteQueueNode(nodeSize);
		tail = tail->next;
		inString += l;
		length -= l;
	}
}

unsigned int ByteQueue::Get(byte &outByte)
{
	int l = head->Get(outByte);
	if (head->UsedUp())
	{
		ByteQueueNode *temp=head;
		head = head->next;
		delete temp;
		if (!head)  // just deleted the last node
			head = tail = new ByteQueueNode(nodeSize);
	}
	return l;
}

unsigned int ByteQueue::Get(byte *outString, unsigned int getMax)
{
	unsigned int getMaxSave=getMax;
	ByteQueueNode *current=head;

	while (getMax && current)
	{
		int l=current->Get(outString, getMax);

		outString += l;
		getMax -= l;

		current = current->next;
	}

	while (head && head->UsedUp())
	{
		current=head;
		head=head->next;
		delete current;
	}

	if (!head)  // every single node has been used up and deleted
		head = tail = new ByteQueueNode(nodeSize);

	return (getMaxSave-getMax);
}

unsigned int ByteQueue::Peek(byte &outByte) const
{
	return head->Peek(outByte);
}

ByteQueue & ByteQueue::operator=(const ByteQueue &rhs)
{
	Destroy();
	CopyFrom(rhs);
	return *this;
}

bool ByteQueue::operator==(const ByteQueue &rhs) const
{
	const unsigned long currentSize = CurrentSize();

	if (currentSize != rhs.CurrentSize())
		return false;

	for (unsigned long i = 0; i<currentSize; i++)
		if ((*this)[i] != rhs[i])
			return false;

	return true;
}

byte ByteQueue::operator[](unsigned long i) const
{
	for (ByteQueueNode *current=head; current; current=current->next)
	{
		if (i < current->CurrentSize())
			return (*current)[i];
		
		i -= current->CurrentSize();
	}

	// i should be less than CurrentSize(), therefore we should not be here
	assert(false);
	return 0;
}

NAMESPACE_END
